"Real time" ultrasonic imaging of organs in a living organism, e.g., a heart in a living human body, has become a well accepted diagnostic tool which for many particular conditions either supplements or replaces instruments that rely on invasive techniques, such as catheterization, or more harmful media, such as x-rays. Real time transcutaneous images of in vivo human anatomy using the relatively harmless ultrasound medium, which makes clear the spatial aspects, i.e., the stereo or perspective aspects, of the image generated reveals information which is even more useful for the assessment of medically significant information. In other words, the addition of a third dimension to the already highly useful "monaural" ultrasonic images introduces another valuable diagnostic aspect.
The ultrasonic stereo imaging system described and illustrated here is specifically designed for medical diagnostics, and therefore, the description is made in connection with this most demanding application. It will be particularly understood, however, that the structures and principles are applicable in many other uses of acoustic imaging as well as to the generation of real time stereo images in any energy modality used for imaging purposes, i.e., optical, infrared, ultrasonic, etc.
A first use of the system is in place of a monaural focusing and deflecting system such as that shown, described and claimed in U.S. Pat. No. 3,913,061, issued Oct. 14, 1975 to Philip S. Green and assigned to the assignee of the present invention. Consequently, the stereo imaging system is shown and described in that setting. Since that patent and the patents referred to therein discuss the problems which are addressed and solved by the monaural system, the information is not repeated here. The subject matter of those patents, however, is specifically incorporated herein by reference. For example, mode conversion problems at liquid/solid interfaces are discussed in U.S. Pat. No. 3,913,061 and U.S. Pat. No. 3,982,223, issued Sept. 21, 1976 to Philip S. Green and assigned to the assignee of the present invention. Therefore, the mode conversion problems are not discussed again in this specification, even though the same acoustic lens arrangement found in U.S. Pat. No. 3,982,223 is applicable in the present imaging system. Similarly, a converter array used to convert the stereo image field pair generated by the system disclosed here is shown, described and claimed in U.S. Pat. No. 3,971,962, issued July 27, 1976 to Philip S. Green and assigned to the assignee of the present invention (also cited in U.S. Pat. No. 3,913,061). The present focusing and deflecting system is designed specifically to be used with such an array; it should be apparent, however, that its usage is broader. Further problems in the conversion of the image fields to viewable condition are addressed in U.S. Pat. No. 4,061,415, issued Dec. 6, 1977 to Jon C. Taenzer and assigned to the assignee of the present invention, and the subject matter of this patent is also incorporated herein by reference.
Like the monaural system of U.S. Pat. No. 3,913,061, the present stereo system provides an ultrasonic image focusing and deflection system for focusing an ultrasonic compressional image on a surface, e.g., a plane or the surface of the segment of a sphere, and for cyclically displacing all points on the compressional image field surface so that they all pass a line whereby the entire image field may be converted by a single line array of transducer elements to a signal capable of use in presenting a visual image. Further like the monaural system, the embodiment of the image deflection system illustrated is intended for use in liquid media and is provided with two or more solid lens elements and a pair of image deflection elements which include therebetween a liquid filler medium. The image deflection elements constitute a pair of coaxially positioned prisms or wedges which are simultaneously rotated in opposite directions so that the transmitted image field is moved past a given line (stationary array of transducers) twice for each full rotation of the prisms.